Automatic transmission controls



Oct. 6, 1959 Filed Aug. 13, 1958 J. J. DUFFY AUTOMATIC TRANSMISSIONCONTROLS 2 Sheets-Sheet 1 JAMES J. DUFFY INVENTOR.v

A TTOPNEYS OGL 6, 1959 J. J. DUFFY AUTOMATIC TRANSMISSION coNTRoLs FiledAug. 13. 1958 2 Sheets-Sheet 2 United States Patent O M AUTOMATICTRANSMISSION CONTROLS James J. Duffy, Detroit, Mich., assignor to FordMotor Company, Dearborn, Mich., a corporation of Delaware ApplicationAugust 13, 1958, Serial No. 754,745

6 Claims. (Cl. 74-732) My invention relates generally to a powertransmission mechanism and more particularly to an automatic controlsystem for controlling the operation of fluid pressure operated servoswhich form a part of the transmission mechanism.

The power transmission mechanism to which the improvement of myinvention may be applied may be used in a power train for an automotivetype vehicle for transferring torque from the vehicle engine to thevehicle traction wheels. The transmission includes cooperating gearelements, and clutch and brake members may be provided for controllingthe relative motion of the gear elements and for providing a drivingtorque reaction. The above mentioned servos are used for the purpose ofenergizing the clutch and brake elements and the servos in turn may bepressurized by means of a iiuid pressure source and interconnectingconduits.

I contemplate that the iluid pressure source may comprise two positivedisplacement pumps, one pump being drivably connected to a vehicleengine and the other being drivably connected to a driven portion of themechanism, such as the transmission tailshaft.

The gear elements of the transmission may be conditioned by the servosfor either forward or reverse torque delivery, and during reverseoperation the tailshaft driven pump is operated in a reverse directionwhile the engine driven pump is continuously driven in a forwarddirection during both reverse and forward drive operation.

A pressure regulator valve mechanism is provided in the control systemon the discharge side of the pumps and a pair of check valves issituated in the structure for establishing or interrupting communicationbetween the regulator valve mechanism and either one or the other pump.

The mode of operation of the check valve is determined by the relativepressure ratio of the pumps. During normal forward driving operation the,engine driven pump functions as thevsole source of control pressure andthe check valves are appropriately positioned to permit the regulatorvalve mechanism to functionally cooperate with the engine driven pumpand to establish a control pressure in the system. At higher operatingspeeds and when the transmission is conditioned for direct driveoperation, the discharge pressure for the tailshaft driven pump may beof a sumcient magnitude to cause the check valves to establishcommuncation between the tailshaft driven pump and the regulator valvewhereby the tailshaft driven pump functions as the sole pressure source,the regulator valve being adapted to exhaust the engine driven pumpunder these conditions.

The inlet side of each of the pumps communicates with a common sump andduring forward drive operation each pump draws uid from the sump underatmospheric pressure and pressurizes the same as above described.However, duringreverse drive operation the tailshaft vis driven in areversedirection and it thustends to feed fluid from 'the circuit intothe sump while the engine driven pump functions as the solel pressuresource. Since variabout the geometric axis thereof. respective convertermembers are joined by innerand f 2,907,232 Patented Oct. 6, 1959 ousexhaust 'ports are provided in the circuit, there is a tendency duringreverse drive operation for the tailshaft driven pump to draw air fromthe control circuit and to discharge'the same to the sump therebycreating an undesirable aerated condition of the oil in the sump. Theaerated oil will be drawn intothe inlet side of the engine driven pumpand this causes the engine driven pump to lose capacity, the operatingcontrol pressure level thereby being decreased. This loss in controlpressure in turn reduces the capacity of the transmission servos andresults in slippage of the transmission clutch and brake components.This condition causes erratic reverse drive performance. Also, until thesystem is purged of aerated oil following operation in reverse,subsequent operation in the forward drive'range is also erratic. Such acondition cannot be tolerated in an automotive type automatictransmission.

I have successfully overcome this problem by providinging an improvedvalve arrangement which cooperates with the two pumps in such a way thatthe tailshaft driven pump is continuously supplied with tluid regardlessof the direction of rotation of the tailshai't thereby eliminating thetendency to pump air into the sump.

The provision of an improved control system for a power transmissionmechanism of the type above described beinga principal object -of myinvention, it is a further objectof my invention to provide a controlsystem capable of establishing forward and reverse torque delivery pathswherein the system includes a dual control pressure source and valveelements cooperating therewith for establishing a continuous fluidpressure distribution path to uid pressure operated portions of themechanism regardless of the relative pressure ratio of the pumps or therelative directions of rotation thereof.

It is a further object of my invention to provide a control systemasabove set forth wherein the pumps have a common fluid supply sump andwherein means are provided for preventing aeration of the sump when oneof the pumps is operated in a reverse direction.

For the purpose of more particularly describing the principal featuresof 'my invention, reference may be made to the accompanying drawings inwhich:

Figure 1 is a cross sectional assembly view of a multiple speedautomatic power transmission mechanism capable of being used in thepower train of an automotive type vehicle; l

Figure 2 is a schematic diagram of an automatic control circuit capableof being used with the transmission mechanism of Figure 1 for obtainingautomatic speed changes, and; g

Figure 3 is an enlarged view of al check valve which functionallycooperates with the dual pressure source,

said pressure source and the cooperating valve forming a part of thecontrol circuit of Figure 2.

Referring rst to Figure l, the transmission mechanism comprises ahydrokinetic torque converter generally designated by numeral 10 and acompound planetary gear unit generally designated by numeral A 12. Theconverter 10 andthe geary unit 12 are situated in spaced 22, a turbinemember 24 and a reactor member 26, saidV converter members eachcomprising a plurality of iluid directing blades disposed' in angularlyspaced relationship The blades forthe outer shrouds which :define atoroidal Aud flow path for accommodating a circulation ofthe workperforming uid. The pump member 22 includes a pump shell Z8 secured to adrive plate 30 by means of a continuous peripheral weld 32. The .driveplate .3.0 in turn may be connected to the crankshaft of the vehicleengine, not shown.

. The inner .periphery of pump -shell 2S is .secured to `a supportingshaft 34 which extends axially into a cooperating opening .formed inWall 16 of .the transmission casing. A positive displacement pump is`positioned within a .suitable pump recess formedin wall 16 as `in;licatcd at .36. The .pump illustrated in .Figure lis of theslipper typealthough other .forms of positive displacement pumps may be used, suchas .a lgear .pump vvhaving cooperatinginternal and external gears. The.pump includes arotor 38 having peripheral slots within `which slippers40 are situated, said slippers forming the working elements of the pumpmechanism as the rotor 38 is driven bythe shaft 34. It is Ythus apparentthat `the pump 36 will be continuously driven by the vehicle engine in.a direct and positive fashion during operation of the transmissionmechanism.

The outer shroud for the turbine member 24 is positively connected to ahub member 42 which in yturn vis splined to an intermediate ipowerdelivery shaft 44.

The radially inward shroud for reactor member 26 is formed with acentral opening within which is positioned an overrunning brake 46having inner and outer .races 48 and 50, respectively. Thrust elements52 and 54 are disposed on either side of the `overruning brake 46 asindicated. The inner race 50 of the overrunning clutch 46 is splined toa stationary reactor shaft 56 which is formed integrally with astationary adaptor 58. Adaptor 158 vin turn is secured to the wall 16and forms a closure for the pump chamber of the pump 36. Wall .16 alsoincludes an extension 60 which `forms the vbearing support for a clutchcylinder member 62, a :suitable bushing .64 being provided for thispurpose.

The member 62 denes an annular cylinder .66 Within which is positioned acooperating annular piston 68. The periphery of member 62 defines abrake drum 70 about which a brake band 72 is disposed.

A clutch member 74 is splined to shaft 44 and the periphery thereof isadapted to .carry clutch discs as indicated, said clutch member 74 andthe clutch .discs beingV formed with cooperating internal splines in :aconventional fashion. The interior portion .of the brake drum 70 is.internally splined and externally lsplined clutch discs cooperatetherewith to partly define a multiple disc clutch assembly. The discscarried byV clutch member 74 and the Ldiscs secured to drum 70 aresituated in alternate relationship and the assembly defined therebyis.identitied by numeral 76.

lThe piston 63 is normally urged in a left-hand direction, as viewed inFigure l, by a clutch return spring 78, said spring being seated on aspring seat element 80. The piston 655 and the cooperating cylinderdefine va working chamber and pressurized fluid may be admitted intothis chamber through suitable internal passages Vto create a clutchenergizing force.

A second clutch member 82 is positively connected to element 70 and itacts as a reaction element for the multiple disc clutch assembly 76.

The gear unit 12 comprises a pair of sun gears of differential diameter.The smaller ofthe sun gears is connected to clutch member 82 and isdesignated by numeral 84. The other sun gear, which is .shown at 36, isformed on or joined to shaft 44 in adjacent relationship relative to sungear 84. The gear unit 12 further includes compound planetary gearsconsisting of long planet pinions 83 and short planet pinions 90. Theplanet pinions 90 are drivably engaged with sun gear S4 and with a ringgear shown at 92 and the short planet pinions 88 engage sun gear 86.Planet pinions .88 and 9.0 are also in mesh `with each other. Both theplanet pinions 88 and 90 are carried by a common carrier assemblyidentied by numeral 94, the carrier assembly including pinion shafts 96and 98 upon which pinions 92 and 90, respectively, are rotatablyjournaled.

.The ring gear 92 forms a part of a brake member in the form of a drum100 and a reaction brake band 102 is disposed about drum 100. Asvalready indicated, suitable servos are provided for each of the brakebands 72 and 102 and these servos will subsequently Vbe described.

The brake `drum 100 .includes a hub portion 104 journaled on anextension 106 which in turn forms a part of an adaptor 108. Thetransmission casing 14 includes an end wall 110 and the adaptor 108 maybe secured thereto by suitable bolts 112.

The adaptorA 108 is recessed to define a pump chamber for accommodatinga pump mechanism 114 of the positive displacement type and a closureplate 116 is provided for yenclosing the pump chamber. The pumpmechanism 114 may be similar in form to the above described pump 36, andthe driving element thereof is positively keyed or `otherwise secured.to the transmission tailshaft, which is identified in Figure 1 bynumeral 11S. The tailshaft 118 in turn `extends .to the rear of thetransmission mechanism and is journaled Within the extension 106. Thecarrier assembly 94 of the planetary gear unit 18 is positivelyconnected to tailshaft 118 to form a power output connection. A governorvalve assembly 120 is positively connected to tailshaft 118 in order toprovide a tailshaft speed signal for control purposes, said valve 120forming a portion of the automatic control circuit subsequently to bedescribed.

The transmission mechanism illustrated in Figure 1 iS capable .ofproviding two forward driving speed ratios and a reverse driving ratio.'To condition the transmission mechanism for a low speed driving ratio ofmarrimum torque multiplication, the brake band 70 may be energizedthereby anchoring sun gear d4, the clutch dise assembly 76 and brakeband 102 being-de-energized. The engine torque delivered to pump memberS2 establishes a toroidal circulation in the converter and this resultsin an increased turbine torque which is transferred directly to sun gear`86 through the power delivery shaft 44. Sun -gear 86 drives pinions 88and the dri-ving motion thereof is transferred to the transmissionpinions 90. Since `sun gear 84 is held stationary, the rotary kmotion ofpinions 90 causes the carrier assembly 94 andthe tailshaft 11S to rotatein a forward direction at a reduced speed ratio.

To obtain a second speed direct drive operation Vthe brake band 72 isdisengaged and the clutch disc assembly 76 is energized, the operationof the brake band 72 and the clutch disc assembly 76 being synchronizedby the automatic control system in a fashion which will be subsequentlydescribed. After clutch disc assembly 76 is sufficiently energized, thesun gears 84 and 86 become locked together for joint movement. It isthus apparent that the elements of the planetary gear unit 12 willturnas a unit 1to establish a direct drive connection between turbine member24 and tailshaft 118.

To obtain reverse drive, the brake band 72 and the clutch disc assembly'76 are both deenergized and the Y brake band 102 is energized. The ringgear 92 is therefore held Vstationary by brake band 102 and the turbinetorque which is transferred to sun gear d6 tends to rotate pinions 88.The rotary motion .of pinions 8S is vtransferred to pinions 90 andVsince the transmission sun gear 92 is held stationary, the pinions 90tend to ride around ring gear 92 in a reverse direction, therebyproviding a reverse driving torque to carrier assembly 94 and tailshaft113.

Referring next to Figure 2, the principal components of the automaticcontrol circuit'for the transmission mechanism of Figure ll are'identified vby appropriate labels. The engine driven pump 36 isprovided with a discharge. passage. 120. andi the intake sidex of pump365 communicates with the aforementioned sump 202.l An oil' screen. maybe provided around the oil` intake passage for the pump 36. asindicated.

A main regulator valve is generally identified by numeral 122 and itcomprises amultiple land valve spool 124 sli'dably situated. within acooperating valve opening, valve spool. 124 having spacedv valve landsidentified by numerals 12.6,-y 128, 130.' and 132. The passage 120communicates with the. valve chamber of the regulator valve 122 andvalve land 126 controls the degree of communication between. passage:120y and an exhaust passage 134.. Passage 120 also communicates with acontrol. pressure; passage: 13.6 and aone-wayl check valve 138 isprovided.. as shown, for establishing direct fluid communication betweenpassagesl 1'20 and.13`6. Checlc valve. 133 is` normally urged towardfaclosed' position by a valve spring 140 ast-indicated.

. The fluid. pressure transferred to pressure passage 136k isredirected. to the regulator valve chamber at a region between' valvelands; 12st and130 and. betweenvalve. lands` and 132. The diameter of'valve land 132 is smaller than the adjacent valve land 130 and thecontrol pressure in; passage: 13.6.- is therefore effective to force thevalve element 13.4. inA an upward. direction.. This upwardly' directedvpressure force; opposes and balances. ai. downwardly directed. spring;force established by valve springA 1.42-Which acts; di'rectlyonxthevalve spool` 124.. It is thus; apparent that. the pressure. establishedin passages 120; andi 1-36. will be. determined by the: valve. spring'1.42,.'

The: discharge sidef of the tailshaft driven. pump 114 communicates withcontrol passage 13.6 through a. pas- -sage.144. A one-Way check. valvegenerallyv designated'.

by numeral. 1146 is situatedzinpassage 144 and isv adaptedltoaccommodate the transfer: of; pressurized fluidi fromxthe. pump 114 topassage 13.6; and to inhibit. the transfer of pressurized: fluid. inithe opposite. direction. Valve 146 normally' assumes a. closed position;under the inuence of springgpressure..

Under those operating.r conditions: in which the dis.- charge.-pressure. for the. pump: 36 is greater than the.- discharge pressure;for.' pump. mechanism 114,. the. one-Way' checlc valve.- 146 will be:closed and one-Way check valve 138- will beropened, andzpressureregulation by theregula.-A tor valve 122 Will be effected by valve land126. However, under those driving: conditions in which the'dischargepressure for pump mechanism 114 is. greater'than. the discharge;pressure for-pump 3.6, the.; check valve. 138'. will assumeV a closedposition and check valve 146willbe opened. Communication is therefore;establishedbetween passages` 14.4: and', 136, thereby permittingthe,pump:

mechanism 11.4 tot supply` the` pressure requirements forthe. entirecircuit.. Under these conditions; the contrai.

pressure.` in; passage 136V is: distributed. to the regulator valvechamber in the; region between valve. lands. 12d and. 13.0, asuitahle;port 148 beingprovided for this purpose.

As soon as. valve 138 closes, thevalve; spool 124 will be. shifted in.an upward direction'. so. that, valve? land 128 will control the degreeof communication. between port 148 and. theA exhaust* passage 134;v Uponmovement. of the valve spool 124- toanupward position in this. fashion,valve. land 126 is shifted'v soA that the discharge passage 120 isbrought.. into direct.' communication with. exhaust.

passage. 134-, thereby rendering the pump 36 inoperative. Since the.pumpv 36 operates with a substantially.` zero pressures diferential, aconsiderable. saving in. pumping horsepower is. obtained'.

It is contemplated. that the. pump. mechanism 114 will be. capableY of.supplying the total. requirements; of the circuit only' at'v very highspeeds' during' operation in the aforementioned: direct drive ratio.However, the check. valve 146 and the check valve 13% may both beopened. during operation at an intermediate. speed range so that.

the pump mechanism 1.141will supplement the operation of' the pump 36.

The hydrokinetic torque converter l*I0L is suppliedfwitliv'.

y also supplies the lubricating'passages in the trans-f' missionmechanism as schematically shown at 1'52 and an orifice 154' is disposedbetween passage 150 andi` the exhaust region in order to maintain adesired back pres sure in passage 150. The magnitude of the backpressure is controlled by a pressure relief valve 156.

A converter fluid Yreturn passage is shown at 158 and itl communicateswith an oil cooler 160i throughv a check valvemech'anism 162.

Passage 136. extends' to a manual valve generally shown at 164, saidmanualv valve including a valve spool 166 having spaced valve lands168', 1'70 and 172, the passage' 136v communicating with the manualvalve at a region between valve. lands 170and 172'.

The manual valve 164 may be adjusted tov anyA of severaloperatingpositions tov select thev various drive ranges, said drive ranges: beingidentified' by the. symbols R, N, D and L which respectively correspondto reverse, neutral, drive and. low. When thejvalve spoolV 1`66-as1sumes the position shown in Figure 2,.the transmission will beconditioned for operation in driven range.

A. shift valve is generally identified in Figure 2 by numeral 174 and itcomprises. avalveelement 176 having spaced valve lands 173 and 180.. iValve element 176 isf disposed in. a. cooperating valve. chamber and' isurgedV in an upward. direction, as; seen in Figure 2^, by af valverspring 132. A. passage: 134 extends freni. the manual. valve chamber toan intermediate region of'thershiftlvalve. chamber and. when the manualvalve is in the position shown, passage 123:4 is. in. communication.with. passager' cates with a'. passage 190 through anorificecontrolavalvef' generally identitidy in. Figure 2' by numeral1192. The' passage 1920 in. turn communicates with" one side. of a..fluid pressurev operated. servo: for. the. brake; band 72.A This servo.comprises a cylinder 194- and a cooperating.y

piston 196, said piston and cylinder' cooperating to define.-

a pairv of opposed' workingchambers. The piston 196'; is connected tothe brake bandk 721 and a retracting position as indicated..

The aforementioned passage 19.0Lcommunicateswit1r the.. working chamberon the release sideA of thepiston 196. The working chamber on the applyside-'of pistonv 196 communicates with a passage-.198which extends: tothe manual valve and. which communicates with control: pressure passagethrough the manual valve. It is. thus apparent that when both. of theopposed working chambers of` the brake servo defined and piston 196 arepressurized, 'the brake band 192- will be released. However, when theworking chamber' onV the release side or" the piston 1-96 isexhaustedf,the brake band 72 will be applied. i

The brake band 102v is also energized by 'means'V ofl a uid pressureoperated servo. which is defined by'a cyl"- cates with a passage 204extending to the manual valve.`

spool. When the manual valve spool 166- is inthe posi*Y tion shown,passage 204 communicates withz-the; manual-fv valve chamber between`valve lands.16& arurlk 170 'which'.

by cylinder 1.94-

nturn is exhausted through au associated exhaust port as indicated.

t The'shiftvalve 174 includes a portion 206 situated at the upper end ofvalve element 176 which includes a relatively large diameter valve land208. The upper side of land 208 is subjected to a vehicle speedsensitive governor pressure which is supplied thereto by a communicatingpassage 210, said passage extending to the previously described governorvalve mechanism generally Idesignated by the numeral 119. As best seenin Figure 1, valve mechanism 119 comprises a valve element 212 situatedin the previously described opening on one side of the axis of rotationof tailshaft 118. The opening in which valve element 212 is situatedcommunicates with an exhaust port 21,4 and the valve element 212 isurged under the influence of centrifugal pressure to a radially outwardposition, thereby tending to close exhaust port 214. The opening forvalve element 212 communicates with port 214 and the passage 210 extendsthereto as indicated in Figure 2. e

The passage 210 also communicates with passage 144 through a owrestricting orice 216. The pressure in passage 210 exerts a radiallyinward force on valve element 212 which opposes and balances thecentrifugal force acting in the opposite direction. It is apparent thatcommunication between passage 210 and exhaust port 214 will bedetermined by the speed of rotation of the tailshaft, and the pressurein the passage 210 will be a function of the tailshaft speed. The orice216 establishes. the desired amount of back pressure in passage 144 sothat pump mechanism 114 may be utilized as a sourceY of control pressureas previously described. This is important during reverse driveoperation.

The governor pressure force acting on shift valve 174 is opposed by amodulated throttle pressure force which acts in an upward direction onvalve land 180 and on arditferential area formed on the lower side ofland 208. Pressure is distributed to the region of the valve land 180andland 208 through modulated throttle pre'ssure passage 218.

A throttle pressure modulator valve element is shown at 220 and it isurged in a downward direction, as seen in Figure 2, by a valve springwhich acts against the valve element 176- Throttle pressure isdistributed to one side of the modulator valve element 220 through amodulated throttle pressure passage 222 and when the shift valve 176assumes an upward position, the modulator valve element, 220 is used toestablish communication between passages 222 and 218 thereby creating areduced ormodulated throttle pressure in passage 218. It is thisreduced'throttle pressure which is utilized for determining the shiftpoint.

' The previously mentioned throttle pressure is passage 222 is producedby a throttle valve mechanism generally identified by numeral 224. Thisvalve mechanism 22,4 comprises a valve spool 226 having spaced valvelands 228 and 230. Valve mechanism 224 further includes adownshift valveelement 232 having spaced valve lands 234 and 236. A spring 235 isinterposed between valve elements 232 and 236 so that when the former isadjusted, a valve actuating force will be transmitted to valve element226. The movement of valve 232 is proportional to engine throttlemovement and a mechanical connection between the engine throttle andvalve element 232 may be provided for obtaining this adjustment.

Control pressure is distributed to the throttle valve mechanism by thelands 228 and 230 by means of a passage 238, and valve landv 230 isadapted to control the degree of communication between passage 238 andthe aforementioned throttle pressure passage 222. An annular workingarea is formed on one side of valve land 230 on which the pressure inpassage 222 is caused to-act. This creates a pressure force whichopposes and balances the force supplied by valve spring 235. Movementofthe engine throttle toward awide open position 8 f willcause compressionof spring 235 and this results in a high throttle pressure in throttlepressure passage 222.

It is thus apparent that the magnitude of the throttlev pressure inpassage 222 will be proportional to engine torque demand.

For the purpose of explaining the mode of operation of that portion ofthe control circuit thus far described, it will be assumed that theselector valve is positioned as shown in Figure 2 and that the vehicleis operated from a standing start. The governor pressure in passage 210will be Zero when the vehicle is stationary, and if the engine throttleis relaxed the throttle pressure in passage 222 is also substantiallyzero. Since the shift valve element 176 assumes an upward position,passage 186 is exhausted through the exhaust port associated with theshift valve 174 and the clutch servo and theworking chamber on therelease side of the brake servo piston 196 are both exhausted, thelatter communicating with passage through passages 186 and 188 aspreviously explained. The working chamber on the apply side of thepiston chamber 196 is pressurized by means of passage 198 and thereforethe low speed brake band 72 is applied.

If the operator then depresses the engine throttle, engine torque willbe transmitted through the converter 10 and through the gear unit 12 inthe manner previously described to provide an over-all driving ratiowith maximum torque multiplication. Operation in the low speed drivingratio continues until the magnitude of the governor pressure in passage210 issuflicient to cause the shift valve element 176 to move in adownward direction against the opposing force of valve spring 182 andthe modulated throttle pressure force. The valve element 176 will thenshift to the position shown in Figure 2 and the vehicle speed at whichthis shift occurs will be determined by the engine throttle setting.

After the valve element 176 assumes the position shown, communication isestablished between passagesV 184 and 186 thereby causing the servo forthe clutch 76 to be energized and the pressure chamber on the releaseside of the brake servo piston 196 to be concurrently pressurized. Sincethe clutch assembly 76 becomes energized in sequence with engagement ofbrake band 22, the transmission is conditionedfor direct driveoperation.

If it is desired to operate the transmission in reverse, manual valvespool 166 can be shifted to the reverse position and passage 198 becomesexhausted through an exhaust port 240 which becomes uncovered by valveland 72. Control pressure passage 136 is brought into directcommunication with passage 204 and the working chamber defined in partby numeral 202 of the reverse piston circuit is therefore pressurized toapply the reverse brake band 102. The clutch assembly 76 is de-energizedsince the passage 186 is exhausted through the exhaust port associatedwith shift valve 174, the valve element 176 assuming an upward positionduring reverse drive operation under the inuence of the spring andmodulated throttle pressure forces. Since the clutch assembly 76 and thebrake band 72 are released while the brake band 102 is applied, thetransmission is in condition for reverse drive operation as previouslyexplained in the description of the transmission structure shown inFigure l.

When the shift valve moves to the direct drive position as indicated inFigure 2 during a shift from low speed operation to normal driveoperation, the valve element 176 causes the modulator valve element 220to move in a downward direction and to block passage 218 While openingpassage 242. Passage 242 extends to the throttle valve mechanism and itcommunicates therethrough with a passage 244 extending to an exhaustport 246 in the manual valve 164. It is thus apparent that the upwardlydirected modulated throttle pressure forces which act on the shift valveelement 176 prior to the shift to the direct drive position areterminated, and the shift ,valvev174 will therefore` maintain a directdrive p'osition'until7 the gov-- ernor.- pressure becomes sufficientlyreduced in magnitude. to-permit the valve 172- to urge the valve 1176 inan upward. direction. The vehicle speed at which this shift t'o the.upward or low speed position occurs will be substantially less than thevehicle speed at which a shift will occur from a low speed upwardposition to the direct drive: downward position.

Itis desirable to delay the application of the low speed brakefband 72during a downshift from directdriveto. the low speed ratio under a zerothrottle condition. This prevents an undesirable roughness when thebrakeY band 72z is applied; This delay is accomplished by thepreviouslymentioned orifice control valve 192. which comprises a: valve:spool 24S having spaced valve: lands Z50-and' 252. Valve spool 248 is'urged in a downward directionby av suitable: valveA spring. The valvespool 248- is slidably positionedv in the valve chamber and the lower.end' there.--

ofis subjectedto throttle pressure by means of' a passage` 254i.Whenever the'engine is under torque; the'throttleA pressure is suicientto maintain spool 248y inthe posi-V tion shown and then freecommunication is establishedV throughv orifice control. valve 192between. passages 188 and' 190i However, under` zero throttle conditionstheA throttle pressure becomes reduced tozero andi the valve spool 248iis moved in a downward position under the. influence.' ofthe associatedvalve spring. When this oc curs. passage E881 communicates with passage190 onlythrough4 a". by-pass orice shown at 256. Whenever a downshiftaoccursunden zero throttle conditions the pressurizedluid in the pressurechamber on the release side ofthe: bralre` ser-.vo piston 196i must' be;exhausted4S through theforiiice. 2`56and1ths delays the application. offthe brake bands217-2relative` to theV time interval required to'-d'eenergize thel clutch. assembly` 76.

It; is: not: desirable toi restrict they degree of communicationbetweenpassages 18S' and 190i during a light throttle upshift since this wouldcause anundesirablev overlapl between the engagement of the' clutchiassembly 76 and the; disengag'ement.ofitheV brakeband 72'; During suchialight: throttle. upshift the valve spool 2481 would" normally assume adownward position and wouldE normally provide such a. restriction. I-have therefore proV-ideda passage 25S- which. byLpasses'. the orificecontrol valve-192'A andwhich permitsipressurized duid to pass directlyfrom passage 18d-'to passage 196 and' into the Working chamber omthe-release si'd'ejof the brake servoA piston 196. I have provided. a:one-way check valve as shown at 226-- to ac commodatethis. direct`transfer of. pressurized fluid tothebrake servo'. During the abovedescribed zero throttle downshift the check valve 260 is eiiectivetoinhibit abypass; flow through passage 258 andthe oric'e 25d-pro videsthe' onlyexlrausti path for the iluid chamber in thereleasey sideV ofthe brake servo-piston 196'.

It is undesirable to` allow the oriiice controlE valve 1592 torestrictth'efluid exhaust path for the low speed brake servo'. when? the vehicleis traveling at relatively high speeds@ and when the manual valve isshifted to a low4 range" position indicated: by the symbol L I havethere'- fore provided a piston element 262 in the lowermost porton ofthe' valve chamber for the oriiice control' valve The lower end of thepiston element 262;' is subjected to cfontrol pressure when the manualvalve assu'm'es the low range position andl this control pressure isdistributed to the orihce control valve through passage 264.. ltis thusapparent that whenever the manual valve is shifted to the low rangeposition, the oritice control valve' element 24S' will' be held; in theupward' position regardless: of the engine throttle position or themagnitudle ofthe engine throttle pressure. rlhe1 brake band 7-21 maytherefore be quickly applied as thek clutch assembly 76.y is disengaged.This prevents an undesirable slippage of. the friction elements.

previously indicated, the transmission maybe corrditioned for continuousoperation in the low speed drive range, bymovingfthe: manual valve to.`the low range; pon? tion' and this.` causes valve.v land 1.72 to uncoverpassage.

264 so. that the latter will-communicate: directly with.co11"I trolpressure passage. 136Y through theA manual. valve.. Passage 264 alsocommunicates with the lowerv endot a; portion: 206 of shift valve;174,`there.byl urging the samer in. an upward' or low speed position.Control pressure. is also distributed. from passage 264 to`r passage 244and# through the throttle valve. mechanism. to-,passage 242.. Thiscauses control pressure to be distributed to thelower: end of valve land180 and to the working area onthe. lower side; of l'and` 208.v Thiscauses an additional pressure force which. urges the. shift valve 174 toa low speed position.. Passage 186 is. therefore brought into: directcommunicationwithr the exhaustport associatedtwith: shift. valve 174 andthe clutch assembly 76 is exhausted directly into passage; 186iSimilarly; the. working chamber.l on the. release. side of. the brake;piston. 196A is. exhausted through passages 190, 188.. and 186,I the.orifice control valve.. 192 assuming' an. upward. position under these:conditions. as. previously explained.

In. order to maintain a smooth shift pattern andA toy maintain. therequired. torque capacity for the various'- clutch and brake servos, itis. desirable to Varythe-magni' tude of. the. control. pressure inaccord with the operating torquei demands. For this reason. acompensator valve mechanism has been included in the circuit, asindicated at. 266. This mechanism-v comprises a. multiple land valvevelement 268` which isv positioned in a cooperating valve: opening andwhich'isr formed with a plurality of opposed valve. lands. shown at 270,272, 274 and 276. The valve element268 is urgedin a right-hand directionby compensator valve spring 278 whichy in turn is seated on a closuremember. 280. Thev region occupied by the spring 278is1 subjected togovernor. pressure. by means of passage 2x1-0 which. communicatestherewith. yControl pressure is dis-- tributed to. the4 compensatorvalve chamber at a point intermediate valve lands 2.70. and 272, thevalve land 2472- supplying. controlled communication between passage2F78' anda compensator pressure passage. 282. Throttle pressure. isconducted to the right side of valve element 268. .throng-hapassage-.28.4.l and it acts. on an annular diiferential area betweenvalve lands 2.74 and. 276. Throttle pressure is also conducted to theleft side of the com"- pensator valve assembly and it acts upon the-fend. of a valve piston elementr 286. A force transfer member 288 is.movably mounted in closure member 280 and is adapted to. engage valve.piston element 286. The force transfer member 288 is urged in aleft-hand directionv by.'y an. inner: valve; spring 29.0 which is seatedat one endthereof. on. aspring. seat element that contacts themem bei:28.8. The other end. of spring 290 acts on valve element 268..

-It is: thus; seen that the: governor pressure force and the: force ofspring 278 acting in a right-hand direction on the: compensator valveelement 268. will be balanced and opposed. by the throttle. pressure.force acting in a left-Y lland direction on Valve land 274. Thisleftwardthrottle pressure force is. supplemented by the force of the.compensator. pressure in. passage 232. which acts on the right side ofland- 272; The compensator valve element 268 therefore; acts as. a`pressure regulator and the compensator pressurewhich is producedinpassage 282 will be afunction of both. governor pressure and throttlepressure; The compensator pressure is transferred to the lower end ofvalve land 1321on1 the regulator valve spool' 124 and' urges they samein anIk upward direction. After throttle pressure is increased inresponse to an increased enginetorque demand for any given vehiclespeed,the compensa-- tor valve element 26Sv will be urged in a left-warddirection to decrease the degree of communication betweenpassages 238and 282. This results in a decreased compensator pressure and the valveland 126- on the regulator valve spooli 124: will therefore provide anncrea-sed' degree oli communication betweenY passages and-1134?.

This results in an increased control pressure which is suflicient toincrease the torque transmitting capacity of the clutch and brake servosto accommodate the increased torque which normally accompanies anincreased engine throttle setting. On the other hand, after the vehiclespeed increases for any given engine throttle setting, the net forceacting on the valve element 268 in a right-hand direction is increasedthereby increasing the degree of communication between passages 288 and232. This increases the compensator pressure and this in turn increasesthe degree of communication between passages 121 and 134. This resultsin a decreased control pressure which is made available to thetransmission clutch and brake servos and this decrease may be made tocorrespond to the inverse relationship between vehicle speed and enginetorque.

The engine torque for any given vehicle speed is generally proportionalto engine throttle setting during movement of the engine throttle from azero throttle position to a throttle setting which is approximately 60percent of the wide open throttle position. After this intermediatethrottle setting is obtained, it is not desirable to allow thecompensator pressure to become decreased since fur- .ther throttlemovement beyond this setting will not ordinarily correspond to anincreased engine torque. A throttle pressure cut-out feature istherefore provided in the compensator valve mechanism. This cut-outfeature is obtained by means of the above described valve piston element286 and its associated spring 290. That is, when the engine throttlereaches an intermediate setting or approximately wide open position, thethrottle pressure will be of a suicient magnitude to cause the valvepiston element 286 to compress spring 290 and to cause the forcetransfer member ZES to engage compensator valve element 268. Upon afurther increase in engine throttle setting, the increase in thethrottle pressure force resulting from the corresponding increasedthrottle pressure will be transferred directly to the compensator valvespool and will oppose and balance the increased throttle pressure forceacting in the left-hand direction on multiple land valve spool element268. The compensator valve mechanism will therefore be renderedinsensitive to changes in engine throttle setting beyond the limitingintermediate position.

A governor pressure cut-out feature is also incorporated in thecompensator valve mechanism and this is provided by a valve pistonelement 292 situated on the right-hand side of compensator valve element268. The element 292 is movably positioned in a cooperating valvechamber and is adapted to engage the end of the valve element 26S.Governor pressure is caused to act on the right side of element 232 andthe left side of element 292 is subjected to control pressure by meansof passage 238 which communica-tes with the associated valve chamber atthis point.

It is desirable to allow the control pressure to decrease as the vehiclespeed increases beyond a predetermined value for any given enginethrottle setting since the torque capacity of the clutch and brakeservos would be insulticient to accommodate the necessary drivingtorque. The element 292 is therefore calibrated so that when apredetermined limiting vehicle speed is reached for any given throttlesetting, the element 292 will be biased against the opposing forces intoengagement with valve element 268. Further increases in vehicle speedwill cause an increased governor pressure but the resulting increasedgovernor pressure force acting on the left side of the valve element 268will be opposed and balanced by an equal force acting on the element292. The compensator valve mechanism is therefore rendered insensitiveto changes in the vehicle speed after a predetermined speed is obtainedfor any given throttle setting.

tv is necessary to increase the control pressure in the circuit duringoperation of the transmission in reverse since the torque requirementsof the reverse brake servo are relatively high. For this reason controlpressure is transferred to the right side of valve land 276 of thecompensator valve element 268 by means of passage 294. The passage 294communicates with passage 204 so that it is pressurized whenever thetransmission is conditioned for reverse drive operation. The pressureforce acting on valve land 276 will supplement the valve forces actingin a left-hand direction of multiple land valve element 268 and willcause a decrease in the compensator pressure passage 282. This in turnwill result in an increase in control pressure as previously explained.

When the transmisison is conditioned in this fashion for reverse driveoperation, the pump mechanism 114 will be driven in reverse directionand the passage 144 will therefore tend to become a pressure `supplypassage rather than a 'pressure discharge passage. The front pump 36continues to be driven in a forward direction and it 'will form the solepressure source during reverse drive. The check valve 146 will thereforebecome closed and the check valve 138 will be opened. The pump mechanism114 will therefore tend to discharge fluid from the control circuit intothe transmission pump and since the circuit includes a plurality ofexhaust ports, there exists a tendency to draw air under atmosphericpressure into passage 144 and to distribute the same into the sump. Inorder to reduce this tendency to pump air, I have provided aprecalibrated orifice in check valve 146 as shown at 294. Orifice 294 isadapted to provide a controlled degree of communication between passage136 and the pump mechanism 114 and the pump 114 therefore dischargesfluid into the sump rather than air. This prevents aeration of the sumpand the oil which is drawn by the pump 36 from the sump will not becontaminated with air bubbles and the regulator valve 122 will thereforemaintain a uniform control pressure in the circuit. The required torquefor the reverse brake servo is therefore maintained. In addition,erratic and unpredictable operation of the control system duringsubsequent forward drive operation is eliminated.

Having thus described a preferred form of my invention, what I claim anddesire to secure by United States Letters Patent is:

1. In an automatic power transmission mechanism having gear elementscapable of Vdelivering torque from a driving member to a driven member;a control system including uid pressure operated servo means for selectively conditioning said transmission gear elements or forward torquedelivery and for reverse torque delivery, a iirst Huid pressure pumpdrivably connected to said driving member, a second fluid pressure pumpdrivably connected to said driven member, conduit structure includingseparate portions extending from each pump to a common portion, saidcommon portion communicating with said servo means, and check valvemeans located in each separate portion of said conduit structure forblocking the separate portion of said conduit structure for one pumpwhen the discharge pressure for the other pump exceeds the dischargepressure for said one pump and for blocking the separate portion of saidconduit structure for the other pump when the discharge pressure forsaid one pump exceeds the discharge pressure for said other pump, bothpumps communicating with a common sump, said check valve means includinga calibrated orifice for permitting a restricted uid liow to said secondfluid pressure pump from high pressure portions of said conduitstructure when said driven member is driven in a reverse directionrelative to said driving member.

2. In an automatic power transmission mechanism having gear elementscapable of delivering torque from a driving member to a driven member; acontrol system including fluid pressure operated servo means forselectively conditioning said transmission gear elements for forwardtorque delivery and for reverse torque delivery, a first fluid pressurepump drivably connected to said driving member, a second uid pressurepump drivably connected to said driven member, conduit structureincluding separate portions extending from the discharge side of eachpump to a common portion, a regulator valve mechanism having twopressure regulating portions, one regulating portion communicating withthe separate portion of said conduit structure `for said rst pump andthe other regulating portion communicating with the separate portion ofsaid conduit structure 'for the second pump, and separate valve meanslocated in each separate portion of said conduit structure for blockingthe discharge side of said one pump when the discharge pressure for theother pump exceeds the discharge pressure `for said one pump and forblocking the discharge side of said other pump when the dischargepressure for said one pump exceeds the discharge pressure `for saidother pump, the intake side of each pump communicating with a commonsump, said check valve means including a calibrated orifice forpermitting a restricted uid flow to said second pump from high pressureportions of said conduit structure when said driven member is driven ina reverse direction relative to said driving member.

3. In an `automatic control circuit, a fluid pressure operated servo, apair of iiuid pressure pumps, conduit structure interconnecting thedischarge side of each pump and said servo, each pump being adapted todeliver fiuid pressure to said servo -upon rotation thereof in a forwarddirection and each pump communicating with a common sump, a check valvemeans disposed in said conduit structure for accommodating thedistribution of pressurized fluid from one of said pumps through saidconduit structure when said one pump is driven in a forward directionand for inhibiting a reverse ow of uid to said one pump when said onepump is driven in a reverse direction, and an orilice forming a by-passpassage around said check valve means, said.

orifice permitting a restricted ow of iiuid to said one pump duringreverse operation thereof thereby preventing aeration of said sump.

4. In an automatic power transmission mechanism having gear elementscapable of delivering torque from 4a driving member to a driven member;a control system including uid /pressure operated servo means forselectively conditioning said transmission gear elements for forwardtorque delivery and for reverse torque delivery, a first uid pressurepump drivably connected to said driving member, a second tluid pressurepump drivably connected to said driven member, conduit structureincluding separate portions extending from each pump `to a commonportion, said common portion communieating with said servo means, andcheck valve means located in each separate portion of said conduitstructure for blocking the separate portion of said conduit structurefor one pump when the discharge pressure for the other pump exceeds thedischarge pressure for said one pump 'and for blocking the separateportion of said conduit structure for the other pump when the dischargepressure for said one pump exceeds the discharge pressure for said otherpump, `both pumps communicating with a common sump, said check valvemeans including a movable valve element and spring means for urging saidvalve element to a blocking position, anda continuously openprecalibrated oriiice formed in said valve element for permitting arestricted iluid flow to said second fluid pump from high pressureportions of said conduit ystructure when said driven member is driven ina reverse direction.

5. The combination as set forth in claim 2 wherein .the check valvemeans for said second pump includes a movable valve element and whereinsaid precalibrated oriiice is formed in said valve element to form acontinuously open by-pass passage to accommodate a restricted fluid flowto said second pump from high pressure portions of said conduitstructure when said driven member is driven in a reverse direction.

6. The combination as set forth in claim 3 wherein said check valvemeans includes a movable Valve element and :a -valve spring, said springbeing adapted to urged said valve element toward a conduit structurerestricting position, and wherein said orifice is formed in said valveelement thereby providing a continuously open ilow restricting passage.

No references cited.

